Safety control for a gas fuel burner



1957 J. w. MILLER 2,776,000

SAFETY CONTROL FOR A GAS FUEL BURNER Filed Sept. 10, 1951 I r l l I INVENTOR.

John -W. M/'//e r ATTORNEYS.

United States Patent() "ice 2,776,000 a SAFETY CONTROL FOR A GAS FUEL BURNER John W. Miller, Lansing, Mich., assignor to Motor Wheel Corporation, Lansing, Mich., a corporation of Michigan 3 This invention relates to a safety control for a gas fuel burner.

Present day gas burners are provided with safety pilots which turn oif the gas in the event that the pilot flame is extinguished. Two common forms of safety pilots utilize either a thermal bulb or a thermocouple: In gas burning equipment when the controls fail to function properly, the burner continues to burn and overheat the system. Overheating also occurs when the natural circulation of the products of combustion of the heating unit are interfered with in some manner. This interference can be caused by a faulty flue or by having the unit choked with soot. If in a gas burning apparatus the flame flashes back and burns as a jet in the venturi tube and then does not blow oft when a full gas flow is established, the burning generally produces consider able soot. If the heater plugs with soot, then the combustion products will flow out underneath the casing and if they come in contact with the controls they will overheat them. As the system overheats, the controls are subject to undue heat and the control continues to hold the main gas supply valve open.

It is an object of this invention to improve on the safety pilot valve system of a gas burner so that whenever the heating system overheats, the control will operate to shut off the gaseous fuel to the burner.

In the drawings:

Fig. 1 is an elevation of a gas burner with a thermal bulb type safety pilot control and provided with the improved feature which is the subject of this invention.

Fig. 2 is an enlarged view partly in section of the thermal bulb type safety pilot system provided with the improvement which is the subject of this invention.

In Fig. 1 there is shown a conventional gas heating apparatus comprising a burner 1 which is supplied with fuel from a gas supply line 2 through a pressure regulator 3 and a fuel control generally designated 4. The pilot burner is positioned adjacent the main burner 1 and is supplied with gaseous fuel from the control 4 through line 6. Positioned adjacent to the burner 5 is a thermal bulb 7 which is positioned in the flame emanating from the pilot burner 5. Thermal bulb 7 is connected by a tube 8 with a chamber 9 in control 4, one wall of which takes the form of a diaphragm 10. Chamher 9, line 8 and bulb 7 are filled with an inert gas such as argon. As long as the pilot burner 5 is lighted, the heat from the pilot flame plays against bulb 7, expands the argon gas in the thermal bulb 7, forces the diaphragm 10 upwardly, and diaphragm 10 acts through lever 11 to hold the automatic pilot valve 14 open, thus permitting fuel to flow from gas supply line 2 through inlet port 15 into the main burner control mechanism 4A and into a chambered member 45 to which pilot burner fuel line 6 is connected. The pressure of the gas flowing through inlet 15 into the control is regulated in a conventional manner before flowing into the burner 5.

2,776,000 Patented Jan. 1, 1957 Valve 14 mounted upon bell crank lever 11 which is valve 14 and thus' completely shuts olf the supply of gas to pilot burner 5 and main burner 1 and the argon gas in bulb '7, when heated by the pilot burner flame, acts at alltimes against diaphragm 10 and bell crank 11 to hold -valve'14 open. The gas burner control thus far described is a conventional and known control. In case anything goes wrong with the control 4 so that the main burner 1 continues to burn and overheat the heating system, then the argon gas in bulb 7 will, of course, maintain valve 14 open, thus making a bad situation worse.

It is an object of this invention to obviate this highly undesirable condition by so modifying the safety pilot system so that valve 14 will close whenever the gas burning apparatus overheats. To this end it is proposed,

other inert gas so that gas control valve 14 will close..

This is accomplished by providing a fusible plug in an orifice or opening communicating with the interior of the chamber 9, tube 8 and bulb 7. The fusible plug can be positioned either in tube 8 or in a wall of chamber 9. By way of illustration, the stationary wall 18 of chamber 9 is provided with a tubular extension 19, the outer end of which is closed by a fusible plug 20. Plug 20 is preferably made of any low fusing solder such as half-andhalf solder (about 50% lead and 50% tin) which has a melting point of 350 F. However, plug 20 can be made of a lower melting point alloy such as Woods Metal which is an alloy comprising bismuth, lead, tin, and sometimes cadmium, and melts in the neighborhood of 65%C. to 111 C. Hence, if for any reason the control 4 fails to function properly or if for any reason the control 4 is subjected to undue heat and overheats, plug 20 will melt thereby exhausting the argon gas from bulb 7, tube 8, and chamber 9, relieving the pressure against diaphragm 10 and spring 16 will immediately close valve 14 thereby shutting off the supply of gas to main burner 1 and pilot 5.

Plug 20 will be made of any known and suitable alloy or other material which will melt whenever the gas burning apparatus reaches an unsafe temperature. The material need not be electrically conducting and therefore can be a low melting point thermoplastic material. For enabling lighting the pilot burner 5 there is provided a pin 43 slidably mounted in the control housing 13 so as to be projectable into engagement with a lever 44. Lever 44 engages lever 11 to rotate lever 11 counterclockwise about pin 12 and against the resistance of spring 16 to open valve 14. Thus, when it is desired to light the pilot burner 5, pin 43 is depressed to open valve 14; and the gas issuing from the pilot burner 5 is ignited. Pin 43 is held in the depressed position for a period of time sufl'lcient to allow the pressure in the thermal bulb 7 and chamber 9 to build up sufiiciently to hold the valve open.

I claim:

1. In a gaseous fuel heating apparatus, a main burner and a pilot burner, a valve controlling the flow of gaseous fuel to said burners, a valve control device comprising a diaphragm operatively connected to said valve means, a bulb positioned in heat exchange relation with said pilot burner, a tube connecting said diaphragm and bulb, and a gas within said tube and bulb which expands when subjected to the heat of said pilot burner to act upon the diaphragm and hold said valve means open, a portion of said valve controlling device being made of a low melting point material whereby whenever said valve is subjected to a predetermined temperature the fusible material will melt and the gas will flow from said bulb whereby the diaphragm is inefiective to hold said valve open and. said valve closest to shut-'off .the;flow of gas; -5

to said burners.

2. The combination defined in claim. 11 wherein'grsaid heating apparatus includes aacasing, saidaburners being positioned within the casing, said valve and. saidifusible; member being positioned without thecasing;

3. The combination defined in. claim 1 wherein: said heating apparatus. includes a combustion chamber, said burners being positioned within the'combustion chamber,

the combustion chamber.

References Cited in the file of this patent UNITED STATES PATENTS Blanchard Dec. 11, 1923 Sladky Nov. 30, 1926 Peters Dec. 1, 1936 Beam Mar. 29, 1938 Betz et al. Dec. 13, 1938 Tornquist Dec. 26, 1939 Simpson Mar. 26; 1940 Hildebrecht -.July, 14, 1942 Mantz June. 13,, 1944" Johnson et a1. Dec. 28, 1948 

